A steering handle for a catheter. The steering handle includes a thumb knob arrangement for driving a cam assembly that in turn actuates a pull wire or pull wires. In some embodiments, the cam assembly includes a set of dual pins that actuate the pull wire in a quasi-linear relationship between cam rotation and axial displacement of the wire. In certain embodiments, the second set of dual pins imparts a reverse action on a second pull wire, also in quasi-linear fashion. That is, when one wire is released by the cam assembly, the other wire is taken in by the cam assembly. In various embodiments, the quasi-linear action can cause release of more pull wire than is taken in, thereby helping prevent the released pull wire to act as an unwanted counter force to the actuated pull wire.